CN107810251B

CN107810251B - Sequential treatment with aqueous sulfonated aromatic polymers and aqueous polyethylene oxides to improve water retention

Info

Publication number: CN107810251B
Application number: CN201680036214.1A
Authority: CN
Inventors: W·于; M·J·拉德勒尔; S-Y·谷
Original assignee: Dow Global Technologies LLC
Current assignee: Dow Global Technologies LLC
Priority date: 2015-06-26
Filing date: 2016-06-23
Publication date: 2020-11-13
Anticipated expiration: 2036-06-23
Also published as: EP3313953B1; EP3313953A1; JP2018522974A; JP6751109B2; WO2016210100A1; CN107810251A; US20180195001A1; US10604702B2

Abstract

The particle aggregates are treated with two different aqueous mixtures, first with an aqueous mixture containing a sulfonated aromatic polymer component and subsequently with an aqueous mixture containing polyethylene oxide.

Description

Sequential treatment with aqueous sulfonated aromatic polymers and aqueous polyethylene oxides to improve water retention

Technical Field

The present invention relates to a method of treating a collection of particles, such as soil, with two different aqueous mixtures to increase the water holding capacity of the collection of particles. One aqueous mixture contains a sulfonated aromatic polymer component and the other aqueous mixture contains polyethylene oxide.

Background

Cultivation in arid and semi-arid climates is challenging because of the difficulty in retaining water in the soil. Increasing demand for crops in global population growth and developing countries and increasing frequency of drought conditions in arid and semi-arid regions require increased water use efficiency in agricultural production. Increasing the Water Holding Capacity (WHC) of the soil in the root zone of plants and retaining the available water capacity of the soil would be beneficial to crop yield. In addition, increasing the WHC helps reduce fertilizer intrusion into the environment and increases fertilizer efficiency.

Incorporation of hydrogel or superabsorbent polymer (SAP) materials as soil additives is one way to increase the WHC of soil. SAP soil additives have been used in horticulture, potting compounds, gardening and some high value crop applications. However, a problem with hydrogel and SAP materials is that they are difficult to deliver into the field. In order to introduce these materials into the root tips of the field, they need to be delivered in granular form and mechanically fed into the field, but that adds an additional level of complexity to preparing the field. Alternatively, the hydrogel or SAP material may be coated directly onto the seed or agricultural synergist (e.g., pesticides and fertilizers). Coating seeds and agricultural synergists with hydrogel or SAP materials also adds expense and complexity to the agricultural process.

It would be desirable to identify a method for effectively increasing the WHC of soil in a manner that is easy to deliver in the field without adding significant complexity or additional expense to the existing materials. It would be particularly desirable to be able to deliver WHC-enhancing additives to soil in the field in the form of an aqueous mixture so that they can be readily incorporated into irrigation systems or ready-to-use aqueous mixture delivery methods. It is even more desirable to identify a way to deliver WHC-enhancing additives as well as agricultural synergists such as fertilizers to the soil in the field in the form of an aqueous mixture.

Disclosure of Invention

The present invention provides a method of effectively increasing the WHC of particulate aggregates such as soil in a manner that is easily transferable in the field without adding significant complexity or additional expense to the current materials and agricultural processes. The present invention provides a method of delivering WHC-enhancing additives in the form of an aqueous mixture to an aggregate of particles, such as soil in a field, thereby making it easy to incorporate them into an aqueous mixture delivery method such as an existing irrigation or fertilization system. The present methods may even include delivering WHC-enhancing additives as well as agricultural synergists such as fertilizers in the form of an aqueous mixture into a collection of particles (e.g., soil in the field).

Surprisingly, it has been found that sequential treatment of particulate aggregates such as soil with an aqueous mixture containing a sulfonated aromatic polymer component and then with a separate aqueous mixture containing a polyethylene oxide material results in an increase in WHC of the particulate aggregates, even beyond the results achieved by treating the particulate aggregates with either of the aqueous mixtures alone. Even more surprising, this synergistic effect does not occur when the aggregates of particles are treated with the same aqueous mixture in the reverse order (that is to say, first with a mixture of polyethylene oxides and subsequently with a mixture containing the sulfonated aromatic polymer component).

In a first aspect, the present invention is a method comprising treating an aggregate of particles with two different aqueous mixtures, first with an aqueous mixture comprising a sulfonated aromatic polymer component and subsequently with an aqueous mixture comprising polyethylene oxide.

The invention can be used, for example, as a method for increasing the water holding capacity of soil for cultivation.

Detailed Description

"and/or" means "and, or". "plurality" means two or more than two. Unless otherwise indicated, all ranges are inclusive of the endpoints. Unless otherwise indicated, "molecular weight" refers to weight average molecular weight as determined by size exclusion chromatography.

Unless date is indicated by test method number in the form of a two-digit number with hyphens, test method refers to the most recent test method from the priority date of this document. The reference test method contains both the reference test association and the test method number. Test method organization is referenced by one of the following abbreviations: ASTM refers to ASTM International (formerly American Society for Testing and Materials); EN refers to European standard (European Norm); DIN refers to the German institute of standardization (Deutsches institute fur Normung); and ISO refers to the International Organization for standardization (International Organization for standardization).

The present invention is a method suitable for treating an aggregate of particles. A particle aggregate is a substance comprising a plurality of particles or grains. For example, sand is a collection of particles comprising a plurality of silica particles. The collection of particles desirably comprises an organic material, preferably organic particles. Soil is an aggregate of particles that comprises a plurality of organic and inorganic particles and in which organisms and/or plant life can grow. There are many different types of soil. The invention is particularly suitable for treating any type of soil.

The process of the invention is suitable for increasing the Water Holding Capacity (WHC) of an aggregate of particles treated in said process. WHC is a measure of the water retention of particle aggregates. The determination of the WHC of particle aggregates using the Water Holding Capacity (WHC) measurement method is described in the examples section below.

The process of the present invention requires treating the collection of particles with two separate aqueous mixtures. "aqueous mixture" refers to a combination of components, one of which is water. The non-aqueous components of the aqueous mixture are desirably (but not necessarily) soluble in water. A component is "soluble in water" if at least 0.01 grams of the component is dissolved in 100 milliliters of water at 23 ℃ to form an aqueous solution. An aqueous solution is a homogeneous distribution of one or more than one component in water. It was determined whether the components were evenly distributed as evidenced by visual inspection of the mixture for no precipitation or phase separation after the components of the mixture were mixed together for 30 minutes. One or both of the aqueous mixtures is an ideal aqueous solution to facilitate coating of the aqueous mixture without the risk of clogging the coating equipment.

The first aqueous mixture is an aqueous mixture containing a sulfonated aromatic polymer component. The sulfonated aromatic polymer component is desirably soluble in water. Examples of suitable sulfonated aromatic polymer components include one or any combination of more than one selected from the group consisting of: sulfonated naphthalene formaldehyde condensates, sulfonated phenol formaldehyde condensates, polystyrene sulfonates, ortho-and para-toluene sulfonamide formaldehyde polymers, and lignosulfonates (lignosulforates). The aromatic rings of the sulfonated aromatic polymer component may include one or more than one alkyl or alkylene group having from one to 18 carbon atoms.

The sulfonated aromatic polymer component is preferably a polymer having a molecular weight of greater than 700 grams/mole (g/mol), preferably 900g/mol or more, more preferably 1000g/mol or more, and can be 1100g/mol or more, 1500g/mol or more, 2000g/mol or more, 5,000g/mol or more, 10,000g/mol or more, 25,000g/mol or more, 50,000g/mol or more, and even 100,000g/mol or more, with no known upper limit on molecular weight, but typically has a molecular weight of five million grams/mol or less, more typically one million or less, and can be 750,000g/mol or less, 500,000g/mol or less, 250,000g/mol or less, 100,000g/mol or less, even 70,000g/mol or less, 50,000g/mol or less, or more, 10,000g/mol or less, 5,000g/mol or less, or 1,250g/mol or less. The skilled artisan can adjust the aqueous character of the sulfonated aromatic polymer component by varying the degree of sulfonation-increased sulfonation results in increased aqueous character. In general, the average degree of sulfonation is desirably 50 mole percent (mol%) or more, preferably 90 mol% or more, and at the same time is usually 100 mol% or less, based on the total number of moles of aromatic groups.

The aqueous mixture containing the sulfonated aromatic polymer component may be a concentrate that is diluted prior to application to the collection of particles, or it may be an aqueous mixture that is readily applied to the collection of particles. If a concentrate, the aqueous mixture may contain 0.1 weight percent (wt%) or more, preferably 0.5 wt% or more, more preferably 1 wt% or more, still more preferably 5 wt% or more and may contain 10 wt% or more, 20 wt% or more, 30 wt% or more and even 40 wt% or more while containing 50 wt% or less of the sulfonated aromatic polymer component, based on the total weight of the aqueous mixture containing the sulfonated aromatic polymer component. When the aqueous mixture containing the sulfonated aromatic polymer component is coated onto the collection of particles, the concentrate of the sulfonated aromatic polymer component is desirably part per million by weight (ppm) or more, preferably 10ppm or more, more preferably 50ppm or more and may be 100ppm or more, 500ppm or more, 1000ppm or more, and even 5000ppm or more, while usually 10,000ppm or less, based on the total weight of the aqueous mixture containing the sulfonated aromatic polymer component.

Desirably, the aqueous mixture of sulfonated aromatic polymer component is provided by mixing together the sulfonated aromatic component and water. Typically the sulfonated aromatic polymer component is not combined with any other components such as agricultural benefit agents when mixed in water. By "unbound" with other components is meant unbound, unattached, and distinct from any other component that can be mixed in water to form an aqueous mixture. For example, if the aqueous mixture contains both the sulfonated aromatic polymer component and the fertilizer, the sulfonated aromatic polymer component does not bind to the fertilizer if both are added separately to the water, as opposed to, for example, adding a fertilizer coated with the sulfonated aromatic polymer component to the water. Similarly, in aqueous mixtures containing a sulfonated aromatic polymer component, a majority (greater than 50 weight percent) of the sulfonated aromatic polymer component is not bound and attached to other components that may be in the aqueous mixture.

The second aqueous mixture is an aqueous mixture containing polyethylene oxide. The polyethylene oxide can be a homopolymer of ethylene oxide, a copolymer of ethylene oxide with other alkylene oxides, or a combination of a homopolymer of ethylene oxide and a copolymer of ethylene oxide with other alkylene oxides.

The copolymer of ethylene oxide may be a random copolymer, a block copolymer, or a combination of a random copolymer and a block copolymer. Suitable alkylene oxides that may be copolymerized with ethylene oxide to form ethylene oxide copolymers include propylene oxide and butylene oxide. Desirably, the ethylene oxide copolymer contains 10 wt.% or more, preferably 20 wt.% or more, of copolymerized ethylene oxide, based on the total weight of the copolymerized alkylene oxide.

Polyethylene oxides are typically initiated with materials having one or more hydroxyl (-OH) and/or carboxyl (-COOH) groups, and may be initiated with materials having one or more amines (-NH)₂) Radical and/or sulfur (-SH) radical. The initiator is typically selected from mono-, di-and triols having from one to 18 carbon atoms. The monoalcohol has a single hydroxyl group. The diol has two hydroxyl groups. Triols have three hydroxyl groups. Examples of desirable monol initiators include 1-dodecanol, butanol, 2-ethylhexanol, n-octanol, decanol, and oleyl alcohol (oleyl alcohol). Examples of suitable diols include ethylene glycol, diethylene glycol, 1, 2-propanediol, 1, 3-propanediol, and 1, 4-butanediol. Examples of suitable triols include glycerol and trimethylolpropane.

The polyethylene oxide may be hydroxyl terminated or partially or fully terminated with a capping group selected from the group consisting of: alkyl or alkenyl having one to 18 carbons, benzyl, halo, or C (O) R, wherein R is alkyl having one to ten carbons. By "partially blocked" is meant that less than all of the terminal hydroxyl groups are blocked.

The polyethylene oxide desirably has a molecular weight of 200g/mol or more, preferably 500g/mol or more, more preferably 1,000g/mol or more, and may be 10,000g/mol or more, 50,000g/mol or more, 100,000g/mol or more, 200,000g/mol or more, 500,000g/mol or more, 1,000,000g/mol or more and even 5,000,000g/mol or more, while usually 10,000,000g/mol or less.

Ideally, the polyethylene oxide is soluble in water. That means that it is desirable to select the molecular weight, end-capping composition, and copolymer ratio so that the resulting polyethylene oxide is soluble in water. The aqueous mixture containing polyethylene oxide is preferably free of water-insoluble polyethylene oxide.

The sulfonated aromatic polymer component and polyethylene oxide tend to interact when present in the same aqueous mixture to form a gel or solution that is sufficiently viscous to be difficult to coat on particle aggregates, such as soil, particularly field soil. Thus, it is desirable that the aqueous mixture containing the sulfonated aromatic polymer component be free of polyethylene oxide. Similarly, it is desirable that the aqueous mixture containing polyethylene oxide be free of the sulfonated aromatic polymer component. Likewise, the aqueous mixture of the sulfonated aromatic polymer component and the aqueous solution of polyethylene oxide are desirably kept separate from each other until during or after the application of the mixture onto the particle aggregate, to avoid gelation before application, which means that these mixtures are used as "two different" aqueous mixtures.

The particle aggregates are treated with two different aqueous mixtures by first treating with an aqueous solution containing a sulfonated aromatic polymer component and subsequently with an aqueous solution containing polyethylene oxide. Surprisingly, it was found that particularly high WHC values are achieved in the particle aggregates when an aqueous mixture of a sulfonated aromatic polymer component is first applied to the particle aggregates and subsequently an aqueous mixture of polyethylene oxide is applied to the particle aggregates. When treating the particulate aggregates with aqueous mixtures in this order, there appears to be a synergistic effect between the sulfonated aromatic polymer component and the polyethylene oxide, which effect increases the WHC compared to the WHC value achieved with either aqueous mixture alone, and which effect does not appear when the aqueous mixtures are applied in the reverse order.

The relative ratio of the sulfonated aromatic polymer component to polyethylene oxide coated onto the particle aggregates is not important in the broadest scope of the present invention. Typically, the weight ratio of sulfonated aromatic polymer component to polyethylene oxide coated onto the collection of particles is 10:1 or less, and can be 1:1 or less, and at the same time is typically 1:10 or more, and can be 1:1 or more (the ratio is "higher" as the first amount is increased relative to the second amount).

Surprisingly, the combination of the sulfonated aromatic polymer component and the polyethylene oxide in the particle aggregate can result in a higher WHC for the particle aggregate than if only one of the sulfonated aromatic polymer component or the polyethylene oxide were coated onto the particle aggregate. Without being bound by theory, the combination of the sulfonated aromatic polymer component and the polyethylene oxide may undergo an interaction known as a CH-pi interaction, wherein alkyl protons of the polyethylene oxide attach to pi-electrons of aromatic rings in the sulfonated aromatic polymer component. This interaction may cause a supramolecular structure between the sulfonated aromatic polymer component and the polyethylene oxide molecules that helps retain water. This structure also results in gel formation if the sulfonated aromatic polymer component and polyethylene oxide are combined in a single aqueous mixture.

Even more surprising, WHC enhancement is achieved by combining sulfonated aromatic polymers and polyethylene oxide, requiring first coating of the sulfonated aromatic polymer component onto the aggregation of particles and then coating with polyethylene oxide. If the two components are applied in reverse order, the enhancement cannot be achieved. Without being bound by theory, if polyethylene oxide is first coated onto the aggregated particles, one hypothesis is that the interaction with the aggregated particles inhibits the polyethylene oxide from achieving a CH-. pi.interaction with the sulfonated aromatic component.

One or both of the aqueous mixture containing the sulfonated aromatic polymer component and the aqueous mixture containing polyethylene oxide may additionally contain other components in addition to water and the polyethylene oxide or sulfonated aromatic polymer component. The other components are desirably soluble in water. Examples of suitable additional components include: anionic surfactants (such as alkyl benzene sulphonates, alkyl sulphates, alkyl ether sulphates, alkyl diphenyl ether sulphonates), nonionic surfactants (such as alkylphenol ethoxylates, straight and branched chain alcohol ethoxylates or alkoxylates, alkylamine ethoxylates or alkoxylates, alkyl polyglucosides), soil corrosion inhibitors (such as water soluble straight chain polyacrylamides), wetting agents and fertilisers (such as fertilisers containing ammonium nitrate and/or one or more elements selected from nitrogen, phosphorus and potassium, sulphur, zinc, iron, copper, boron, manganese, chlorine and molybdenum; preferably urea-containing fertilisers, including urea-containing fertilisers containing one or more elements selected from phosphorus, potassium, sulphur, zinc, iron, copper, boron, manganese, chlorine and molybdenum and ammonium nitrate fertilisers).

It is desirable that the aqueous mixture is free of the reaction product of alachlor and alachlor. Alachlor and reaction products thereof are useful as herbicides and one desirable application of the present invention is to enhance the WHC of soil for agricultural uses such as farming. Alachlor and its reaction products can be undesirable, especially in these applications.

The method of the invention is particularly well suited for agricultural applications where the aggregate of particles is soil in the field. Agricultural processes (such as fertilization and irrigation) have used methods that require application of aqueous solutions to the field, and these processes can be readily adapted to incorporate the present methods. For example, a sulfonated aromatic polymer component and polyethylene oxide may be readily introduced into an irrigation line to increase the WHC of the soil during irrigation. As another example, an existing method of applying an aqueous solution of a fertilizer may be modified to apply two aqueous mixtures as described in the present invention, wherein at least one aqueous mixture additionally comprises a fertilizer. This modified process is used for fertilizer and to increase the WHC of the soil in a single process that is essentially the same as the process of adding fertilizer alone.

Examples of the invention

The following examples are intended to illustrate embodiments of the invention and are not intended to limit the broadest scope of the invention.

Water Holding Capacity (WHC) measurement method

The procedure for measuring WHC of particle aggregates ("samples") such as soil is as follows:

(1) polyvinyl chloride (PVC) vents, scrap and vent (DWV) fittings were provided having an inner diameter of 6.35 centimeters (cm) and a height of 5.74 cm. The weight of a piece of filter paper (Schleicher & Schuell No.0980) was determined and recorded as the "filter paper weight". One end of the adapter was covered with the piece of filter paper (and the filter paper was secured to the adapter with a rubber band to achieve a flat smooth filter paper surface above one end (bottom end) of the adapter).

(2) The weight of the joint with the rubber band and filter paper was weighed and recorded (W1).

(3) The adapter was placed in a 100 x 50 millimeter (mm) crystallization dish with the filter paper covered side against the bottom end of the dish. A 50.00 gram sample was placed in the adapter. The sample surface was smoothed with a spatula.

(4) 100 milliliters (m1) of an aqueous fluid (e.g., water or one or more aqueous mixtures) was slowly applied uniformly over the sample using a dropper. The addition rate is controlled to avoid interfering with the integrity of the sample surface and to avoid spillage of accumulated aqueous fluid on the tip of the adaptor.

(5) An aqueous fluid is flowed through the soil. The water level in the crystallization tray reaches approximately half the height of the sample in the joint. The open portion of the crystallization tray is covered with plastic to prevent water from evaporating from the tray. The adapter with the sample was placed in the pan for 22-26 hours to saturate the sample with aqueous fluid before proceeding.

(6) A12X 12em glass plate was placed on top of an electronic scale (1000 grams of gauge with 0.001g resolution). 6 pieces of grade 2294 filter paper (110 mm diameter from GE Healthcare Life science) were stacked onto a glass plate while ensuring that the pieces of filter paper were flat and free of void spaces between them.

(7) The adapter with the saturated sample was removed from the pan and centered on the top of a grade 2294 filter paper sheet with the filter paper of the adapter assembly abutting the grade 2294 filter paper sheet. 2294 grade filter paper pieces will slowly wick aqueous fluid away from the filter paper and sample of the adapter assembly. Set for 30 minutes, after which the joint with the filter paper and sample is carefully removed and the weight of the weighing reading is then recorded (R1). The adapter with the sample is placed on a 2294 grade filter paper sheet again and set for 10 minutes. Again carefully remove the adapter with filter paper, rubber band and sample and again record the weight read (reading 2). If R2 is the same as R1 (within 0.05 grams) or less than R1, then equilibrium has been reached and you can continue with step (8), otherwise the linker is placed on grade 2294 filter paper sheets for an additional 10 minutes, removed and weighed. Repeat as necessary until two consecutive weight readings are within 0.05 grams of each other or the second reading is lower than the first.

(8) The weight of the adapter, rubber band, filter paper and sample was measured immediately after completion of step (7) to 0.001g, and the weight was recorded as W2.

(9) Grade 2294 filter paper sheets were observed. If grade 2294 filter paper is wet through at its bottom end (i.e., the end near the glass plate), the process is stopped. The process must be repeated with more pieces of 2294 grade filter paper stacked.

(10) The rubber band was removed from the adapter and the sample was transferred to a tared glass beaker. Any sample residue left in the adapter was removed with filter paper and transferred to a glass beaker. Filter paper was added to the glass beaker. The beaker containing the filter paper and sample was placed in a conventional oven at 105 degrees celsius (c) for at least 10 hours (overnight).

(11) The beaker containing the filter paper and sample was set at 21 ℃ and 50% relative humidity for two hours. The combined weight of the beaker, sample and filter paper was measured and the weight of the filter paper and beaker was subtracted therefrom to obtain the weight of the dried sample (W3).

(12) WHC was calculated as the weight percent of water relative to the dry sample according to the following formula:

WHC＝100×(W2-W1-W3)/W3

materials used in the examples

Table 1 lists the compositions of the examples (Ex) and comparative examples (Comp Ex).

TABLE 1

Comparative example A-WHC Using Water

The Water Holding Capacity (WHC) of the soil was determined using a WHC measurement method in which 100 ml of deionized water was used as the "aqueous fluid". The procedure was repeated five times using fresh soil samples. The average WHC of five measurements was 27.8%.

Comparative examples B and C-WHC using an aqueous solution containing a sulfonated aromatic polymer component.

The Water Holding Capacity (WHC) of the soil was determined using a WHC measurement method in which 100 ml of an aqueous solution containing SNFP was used as the "aqueous fluid". For comparative example B, an aqueous solution containing 1000ppm SNFP was used. For comparative example C, an aqueous solution containing 2000ppm SNFP was used. Ppm relative to the total weight of the aqueous solution was measured. The method was repeated twice for each comparative example and the average was taken as the WHC of the comparative example.

The WHC of comparative example B (1000ppm) was 31.2%. The WHC of comparative example C (2000ppm) was 29.7%. Both WHC values were higher than those achieved with deionized water, indicating that SNFP is an additive that enhances WHC.

Comparative examples D and E-WHC using an aqueous solution containing polyethylene oxide.

The Water Holding Capacity (WHC) of the soil was determined using a WHC measurement method in which 100 ml of an aqueous solution containing polyethylene oxide was used as the "aqueous fluid". For comparative example D an aqueous solution containing 1000ppm PEG 8000 was used. For comparative example E an aqueous solution containing 1000ppm WSR 301 was used. Ppm relative to the total weight of the aqueous solution was measured. The method was repeated twice for each comparative example and the average was taken as the WHC of the comparative example.

Comparative example D (PEG 8000) had a WHC of 27.7%. The WHC of comparative example E (WSR 301) was 27.2%. Both WHC values were lower than those achieved with deionized water, indicating that polyethylene oxide alone is not an additive to increase WHC.

Comparative examples F and G-WHC using sequential treatment of an aqueous solution containing polyethylene oxide followed by sulfonation of the aromatic polymer component.

The Water Holding Capacity (WHC) of the soil was determined by first applying 50 ml of an aqueous solution containing 1000ppm of polyethylene oxide and immediately thereafter applying 50 ml of an aqueous solution containing 3000ppm of SNFP using the WHC measurement method. For comparative example F, PEG 8000 was used as polyethylene oxide, and the average of two determinations was taken to calculate WHC. For comparative example G, WSR 301 was used as polyethylene oxide, and WHC was calculated by taking the average of four determinations.

Notably, the total SNFP coated in these assays was equivalent to 100 ml of 1500ppm SNFP, so if SNFP and polyethylene glycol did not work synergistically, it would be expected that WHC would be between the value of comparative example a (31.2%) and the value of comparative example B (29.7%).

The WHC of comparative example F was 27.8%, and the WHC of comparative example G was 30.1%. These values are between or slightly below the WHC values expected for an equivalent amount of SNFP alone and indicate a lack of synergy between SNFP and polyethylene oxide when the soil is first treated with an aqueous polyethylene oxide mixture and then with an aqueous sulfonated aromatic polymer component mixture.

Examples 1 and 2-WHC using sequential treatment of an aqueous solution containing a sulfonated aromatic polymer component followed by polyethylene oxide.

The Water Holding Capacity (WHC) of the soil was determined by first applying 50 ml of an aqueous solution containing 3000ppm SNFP and immediately thereafter applying 50 ml of an aqueous solution containing 1000ppm polyethylene oxide using the WHC measurement method. For example 1, PEG 8000 was used as polyethylene oxide, and the average of two determinations was taken to calculate WHC. WSR 301 was used as polyethylene oxide for example 2 and the WHC was calculated by taking the average of four determinations.

Notably, the total SNFP coated was equivalent to 100 ml of 1500ppm SNFP, so if SNFP and polyethylene glycol did not act synergistically, then WHC would be expected to be between the value of comparative example a (31.2%) and the value of comparative example B (29.7%).

The WHC of example 1 was 33.6% and the WHC of example 2 was 40.8% — both of which were significantly higher than the WHC values of the aqueous solution of the sulfonated aromatic polymer component alone or the aqueous solution of the polyethylene oxide component alone. The results show that WHC is synergistically increased when the soil is treated sequentially first with an aqueous solution containing a sulfonated aromatic polymer component and then with an aqueous solution containing polyethylene oxide.

Claims

1. A method comprising treating soil in a field for agricultural applications with two different aqueous mixtures, first with an aqueous mixture containing a sulfonated aromatic polymer component and subsequently with an aqueous mixture containing polyethylene oxide, wherein the weight ratio of the sulfonated aromatic polymer component to the polyethylene oxide applied to the soil is from 10:1 to 1:10, wherein the sulfonated aromatic polymer component is a sulfonated naphthalene formaldehyde condensate.

2. The method of claim 1, wherein the concentration of sulfonated aromatic polymer component in the aqueous mixture of sulfonated aromatic polymer components is 0.1 parts by weight or more and 10,000 parts by weight or less based on one million parts by weight of the aqueous mixture containing the sulfonated aromatic polymer component.

3. The method of claim 1, wherein the concentration of polyethylene oxide in the aqueous mixture containing polyethylene oxide is 0.1 parts by weight or more and 10,000 parts by weight or less based on one million parts by weight of the aqueous mixture containing polyethylene oxide.

4. The method of claim 1, wherein the polyethylene oxide has a molecular weight of 200 grams/mole or more and 10,000,000 grams/mole or less as determined by size exclusion chromatography.

5. The method of claim 1, wherein the sulfonated aromatic polymer component and polyethylene oxide are both soluble in water.

6. The method of claim 1, wherein one or both of the aqueous mixtures comprises a fertilizer.